The present invention relates to a power monitoring system (or a power range monitor) of a boiling water reactor and particularly to a power monitoring system that monitors the power oscillations of a nuclear reactor core.
In the boiling water reactor (BWR), the output power alternately falls and rises due to the generation and disappearance of voids, respectively, which may possibly generate power oscillations whereby the output power of the nuclear reactor oscillates and is amplified. The widely known reactor core power oscillation monitoring method is to continue operation as long as the soundness of core fuel is secure even in an operating range in which power oscillations occur, and to detect, when oscillations occur that could lead to events affecting the soundness of the core fuel, the oscillations, and safely stop the operation of the nuclear reactor (See, for example, U.S. Pat. No. 5,174,946,the entire content of which being incorporated herein by reference). Also widely known is a reactivity adjustment method that stabilizes the entire reactor core using the above-described method (See, for example, U.S. Pat. No. 5,141,710,the entire content of which being incorporated herein by reference).
High reliability is required to monitor the power oscillations of the reactor core in terms of securing the soundness of the core fuel. However, the problem with the above-described monitoring of power oscillations is that even though oscillations that could lead to events affecting the soundness of the core fuel can be detected when the oscillations occur, necessary measures may not have been taken to secure the soundness of the fuel.